The enhanced interaction between light and photon emitters occurs when the emitters are placed in an optical cavity, where the local density of electromagnetic modes is dramatically increased. In the weak-coupling region, where the emitter-cavity energy exchange rate is lower than the cavity decay rate, enhanced light extraction is obtained from the emitter. More significant effects emerge in the strong-coupling region when the emitter-cavity coupling strength is higher than their individual decay rates, e.g., 2 g>γ or κ (Törmä P and Barnes W L. Rep. Prog. Phys. 2015, 78, 013901), where g is the coupling energy, γ is the emitter scattering rate and κ is the cavity loss rate. In this region, the emitter and cavity coherently exchange energy and lead to the Rabi oscillations, manifesting as a resonant peak splitting in the optical spectra.
High-quality cavities with small effective cavity volume V (g∝1/√{square root over (V)}) and high quality factor Q (Q∝1/√{square root over (κ)}) are expected to support these strongly coupled mixed states for such applications as low-threshold emission (Christopoulos S et al. Phys. Rev. Lett. 2007, 98, 126405; Noda S et al. Nat Photon 2007, 1, 449-458) and ultrafast switching (Volz T et al. Nat Photon 2012, 6, 605-609; Vasa P et al. ACS Nano 2010, 4, 7559-7565; Gunter G et al. Nature 2009, 458, 178-181). The strong coupling has been demonstrated in a variety of optical cavities, including optical microcavities, optical waveguides, and plasmonic cavities. Most of the dielectric-based microcavities suffer from a large cavity volume and active-area footprint. Metal nanoparticles, which support localized surface plasmon resonances (LSPRs) with tremendous electric field enhancement in the deep subwavelength volumes, provide improved mode confinement and coupling strength. Rabi splitting arises from strong plasmon-molecule coupling. Specifically, Rabi splitting in hybrids of plasmonic nanostructures and molecules has attracted intense interests for both fundamental research and applications in sensing, information processing, and nanolasers. Strong plasmon-molecule couplings have been studied in systems comprising molecule aggregates (or single molecules) and plasmonic nanoparticle arrays (or single-particle cavity). Plasmonic switches have been demonstrated based on hybrids of plasmonic nanoparticles and photochromic molecules. However, plasmonic cavities experience intrinsic loss due to resistive heating in metals, which limits the coupling strength between the plasmons and molecular excitons, and impedes the use of plasmonic cavities in long-range optical guiding and switching. To enable long-distance guiding of surface plasmons with strong subwavelength confinement, researchers have been exploring new modes that arise from the hybridization between surface plasmons and dielectric waveguides, which has been achieved in hybrid plasmonic waveguides.
However, the integration of Rabi splitting into the hybrid plasmon-waveguide modes (HPWMs), which have advantages of both subwavelength light confinement of surface plasmons and long-range propagation of guided modes in dielectric waveguides, as remained elusive. The compositions, methods, and systems discussed herein addresses these and other needs.